Insulated gate bipolar transistor

Abstract

An IGBT has layers between emitter and collector sides. The layers include a collector layer on the collector side, a drift layer, a base layer of a second conductivity type, a first source region arranged on the base layer towards the emitter side, a trench gate electrode arranged lateral to the base layer and extending deeper into the drift layer than the base layer, a well arranged lateral to the base layer and extending deeper into the drift layer than the base layer, an enhancement layer surrounding the base layer so as to completely separate the base layer from the drift layer and the well, an electrically conducting layer covering the well and separated from the well by a second electrically insulating layer, and a third insulating layer having a recess on top of the electrically conducting layer such that the electrically conducting layer electrically contacts a emitter electrode.

What is claimed is: 
     
       1. An insulated gated bipolar transistor having layers between an emitter electrode on an emitter side and a collector electrode on a collector side opposite to the emitter side, the insulated gate bipolar transistor comprising:
 a drift layer of a first conductivity type; 
 a collector layer of a second conductivity type different than the first conductivity type, the collector layer being arranged between the drift layer and the collector electrode and electrically contacting the collector electrode; 
 a base layer of a second conductivity type, the base layer being arranged between the drift layer and the emitter electrode, the base layer electrically contacting the emitter electrode; 
 a first source region of the first conductivity type, the first source region being arranged on the base layer towards the emitter side and electrically contacting the emitter electrode, the first source region having a higher doping concentration than the drift layer; 
 a trench gate electrode arranged lateral to the base layer and extending deeper into the drift layer than the base layer, the trench gate electrode being separated from the base layer, the first source region and the drift layer by a first insulating layer, wherein a channel is formable between the emitter electrode, the first source region, the base layer and the drift layer; 
 a well of the second conductivity type, which is arranged lateral to the base layer and extends deeper into the drift layer than the base layer; 
 an enhancement layer of the first conductivity type, which surrounds the base layer such that the enhancement layer completely separates the base layer from the drift layer and the well; 
 in addition to the emitter electrode, an electrically conducting layer, which covers the well, wherein the electrically conductive layer is separated from the well by a second electrically insulating layer; and 
 a third insulating layer, which is arranged on the emitter side on top of the trench gate electrode, the electrically conductive layer and those parts of the base layer, the enhancement layer and the drift layer lying between the trench gate electrode and the well, the third insulating layer having a recess on top of the electrically conducting layer such that the electrically conducting layer electrically contacts the emitter electrode. 
 
     
     
       2. The insulated gated bipolar transistor according to  claim 1 , comprising:
 a second source region of the first conductivity type arranged at the emitter side on the base layer between the trench gate electrode and the well, 
 wherein the second source region extends from the first electrically insulating layer to a border of the second electrically insulating layer, the second source region having a higher doping concentration than the drift layer. 
 
     
     
       3. The insulated gated bipolar transistor according to  claim 1 , wherein the well extends deeper into the drift layer than the trench gate electrode. 
     
     
       4. The insulated gated bipolar transistor according to  claim 1 , comprising:
 a buffer layer of the first conductivity type having a higher doping concentration than the drift layer and being arranged between the drift layer and the collector layer. 
 
     
     
       5. The insulated gated bipolar transistor according to  claim 1 , comprising:
 a first region of the first conductivity type, the first region being arranged on the collector side laterally to the collector layer and having a higher doping concentration than the drift layer. 
 
     
     
       6. The insulated gated bipolar transistor according to  claim 1 , wherein the electrically conductive layer is made of the same material as the trench gate electrode. 
     
     
       7. The insulated gated bipolar transistor according to  claim 1 , comprising:
 a bar of the second conductivity type having a higher doping concentration than the base layer, the bar being arranged at the emitter side in a plane parallel to the emitter side perpendicular to a direction in which the first source region attaches the trench gate electrode and at which bar the first source region, the base layer and the trench gate electrode terminate. 
 
     
     
       8. The insulated gated bipolar transistor according to  claim 7 , wherein the well extends to the bar. 
     
     
       9. The insulated gated bipolar transistor according to  claim 7 , wherein the well is separated from the bar by at least one of the enhancement layer and the base layer. 
     
     
       10. The insulated gated bipolar transistor according to  claim 1 , wherein the electrically conducting layer additionally covers part of the enhancement layer which extends to the emitter side in an area between the well and the first insulating layer, and extends to a region above the base layer, and
 wherein the electrically conducting layer is separated from these layers by the second electrically insulating layer. 
 
     
     
       11. The insulated gated bipolar transistor according to  claim 1 , wherein the drift layer extends to the second electrically insulating layer in an area between the well and the enhancement layer. 
     
     
       12. The insulated gated bipolar transistor according to  claim 1 , wherein the second electrically insulating layer has a thickness between 50 to 150 nm. 
     
     
       13. The insulated gated bipolar transistor according to  claim 2 , wherein the well extends deeper into the drift layer than the trench gate electrode. 
     
     
       14. The insulated gated bipolar transistor according to  claim 13 , comprising:
 a buffer layer of the first conductivity type having a higher doping concentration than the drift layer and being arranged between the drift layer and the collector layer. 
 
     
     
       15. The insulated gated bipolar transistor according to  claim 13 , comprising:
 a bar of the second conductivity type having a higher doping concentration than the base layer, the bar being arranged at the emitter side in a plane parallel to the emitter side perpendicular to a direction in which the first source region attaches the trench gate electrode and at which bar the first source region, the base layer and the trench gate electrode terminate. 
 
     
     
       16. The insulated gated bipolar transistor according to  claim 15 , wherein the well extends to the bar. 
     
     
       17. The insulated gated bipolar transistor according to  claim 15 , wherein the well is separated from the bar by at least one of the enhancement layer and the base layer. 
     
     
       18. The insulated gated bipolar transistor according to  claim 13 , wherein the electrically conducting layer additionally covers part of the enhancement layer which extends to the emitter side in an area between the well and the first insulating layer, and extends to a region above the base layer, and
 wherein the electrically conducting layer is separated from these layers by the second electrically insulating layer. 
 
     
     
       19. A method for manufacturing an insulated gated bipolar transistor, the method comprising:
 providing a lowly doped wafer of a first conductivity type having an emitter side and a collector side, part of the wafer having unamended low doping in the finalized insulated gated bipolar transistor forming a drift layer; 
 applying a mask and introducing a first dopant of a second conductivity type, which is different than the first conductivity type, for forming a well; 
 making a trench recess on the emitter side; 
 coating the trench recess with a first insulating layer and filling the coated trench recess with an electrically conductive material such that a trench gate electrode is formed; 
 forming a second insulating layer which covers the well; 
 forming an electrically conductive layer on top of the second insulating layer; 
 creating an enhancement layer by introducing a second dopant of the first conductivity type and diffusing the second dopant into the wafer using the electrically conductive layer as a mask; 
 after introduction of the second dopant, creating a base layer by introducing a third dopant of the second conductivity type, using the electrically conductive layer as a mask, and diffusing the third dopant into the wafer to a lower depth from the emitter side, into which the second dopant has been diffused; 
 creating a collector layer by introducing a fourth dopant of the second conductivity type on the collector side, and diffusing the fourth dopant into the wafer; 
 introducing a fifth dopant of the first conductivity type using at least the electrically conductive layer as a mask for forming first source regions; 
 applying a third insulating layer on top of the electrically conductive layer, the third insulating layer having a recess on the electrically conductive layer for a contact of the electrically conductive layer to the emitter electrode and a contact opening to the base layer; and 
 applying an emitter electrode and a collector electrode. 
 
     
     
       20. The method for manufacturing an insulated gated bipolar transistor, according to  claim 19 , comprising:
 first applying the third insulating layer on top of the electrically conductive layer such that the third insulating layer laterally extends to the trench gate electrode, the third insulating layer having a contact opening to the base layer; and 
 introducing the fifth dopant of the first conductivity type using the third insulating layer and the electrically conductive layer as a mask for forming first source regions.